Best practice & research. Clinical anaesthesiology
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Best Pract Res Clin Anaesthesiol · Mar 2006
ReviewUse of cerebral monitoring during anaesthesia: effect on recovery profile.
This review article examines the effect of cerebral monitoring using an EEG-based device [i.e. bispectral index (BIS), patient state analyzer (PSA), auditory evoked potential (AEP), cerebral state index (CSI), or entropy] on titration of anaesthetic, analgesic and cardiovascular drugs during surgery. In addition, articles discussing the effects of these cerebral monitoring devices on recovery profiles following general anaesthesia, postoperative side effects, and anaesthetic costs are reviewed.
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Best Pract Res Clin Anaesthesiol · Mar 2006
ReviewSpecial cases: ketamine, nitrous oxide and xenon.
Most general anaesthetic agents produce anaesthesia by increasing the activity of inhibitory gamma-aminobutyric acid type A receptors. The effects of ketamine, xenon and nitrous oxide on these receptors are, however, negligible. These anaesthetic agents potently inhibit excitatory N-methyl-D-aspartate receptors. ⋯ However, xenon decreases the bispectral index in a concentration-dependent manner. Similarly, ketamine and nitrous oxide do not suppress the mid-latency auditory evoked potential whereas xenon does. Thus, anaesthetic depth monitors fail to describe consciousness accurately when ketamine and nitrous oxide are used.
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Sleep stages are conventionally scored according to recommendations by a committee chaired by Rechtschaffen and Kales in 1968. With these rules normal sleep is divided into rapid eye movement sleep and non-rapid eye movement sleep. Non-rapid eye movement sleep is subdivided into four further stages. ⋯ Furthermore, there is considerable interscorer variability, the scoring is time consuming, tedious and difficult to perform. To overcome these limitations automatic sleep scoring devices using processed EEG technology are developed. These developments are discussed in this chapter.
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Best Pract Res Clin Anaesthesiol · Mar 2006
ReviewAltered states of consciousness: processed EEG in mental disease.
Due to increasing life expectancy and a rising elderly population in Europe, the incidence of mild cognitive impairment which may predict diseases like Alzheimer's Disease or Vascular Dementia, is rising. Neurophysiological techniques are simple and inexpensive tools for early diagnosis and provide useful and objective correlates of cognitive activity both in normal subjects and patients suffering from the above conditions. Cognitive impairment due to different mental disease is characterized by decreased power and coherence in the alpha/beta band, which suggests functional disconnection among cortical areas, whereas both power and coherence in the delta and theta bands increase as a sign of cortical deafferentation from subcortical structures. Quantification of power and phase relationship by bispectral analysis suggests the Bispectral Index could be a useful but simple tool for early diagnosis of mental disease.
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This chapter will focus on the two auditory evoked potentials (AEP) most commonly used to assess the effects of general anesthetics on the brain, the auditory middle latency response (AMLR) and the 40 Hz auditory steady-state response (40 Hz-ASSR). We will review their physiological basis, the recording methodology, the effects of general anesthetics, their ability to track changes in level of consciousness and their clinical applications. Because of space constraints, this review will be limited to human studies.